1. Technical Field of the Invention
This invention relates to a substrate processing apparatus and a substrate processing method. More in detail, the invention relates to substrate processing apparatus and method for processing substrates, for example, semiconductor wafers, glass substrates for LCD, etc. with a processing gas, such as ozone gas, the substrates being accommodated in a processing container capable of establishing a closed atmosphere therein.
2. Description of the Related Art
Generally, the manufacturing process for semiconductor devices comprises the following steps of: applying photo-resist on substrates, for example, semiconductor wafers and LCD baseplates; transferring a circuit pattern, which has been scaled down by the photo-lithography technique, to the above photo-resist; developing this pattern; and thereafter removing the photo-resist from the wafers etc. Note, the semiconductor wafers will be simply referred as “wafers”, hereinafter.
As means for removing the photo-resist, there exists a substrate cleaning apparatus. In the prior art cleaning apparatus, the operation to remove the photo-resist from the substrates is accomplished by dipping the wafers etc. into a cleaning bath filled up with a chemical liquid generally called “SPM” (mixture of H2 SO4 and H2O2). To the contrary, there has been a general demand to use a solution of ozone (O3) for the removal operation since its effluent process from a factory is preferable in view of the protection of the environment. In using the solution of ozone (O3) for the removal operation, there is generally employed a cleaning method that the wafers etc. are dipped into a cleaning bath filled up with a solution having ozone melted thereinto, which is so-called “dip” type cleaning method. In this method, the photo-resist on the wafers is oxidized and dissolved into carbon dioxide and water etc. by oxygen atomic radicals in the solution.
Incidentally, according to the above-mentioned method, the ozone gas of high concentration is firstly dissolved into pure water in the form of bubbles thereby to produce the “ozone” solution and thereafter, the resultant solution is supplied into the cleaning bath. Therefore, there sometimes arises a situation that ozone(s) in the solution gradually disappear during the transportation, so that the concentration of ozone is reduced to cause an insufficient removal of the photo-resist. Additionally, the removal operation by dipping the wafers etc. into the ozone solution cannot afford the reaction (oxidation of resist) at high speed. Because, the removal operation is apt to make the quantity of ozone(s) for the resist insufficient although ozone(s) successively disappears as the result of the reaction with the resist.
In place of such a cleaning method for cleaning the wafers etc. by dipping them into the ozone solution, there is newly proposed a cleaning (etching) method for removing the resist from the wafers etc. while using a processing gas, for example, mixture of ozone gas and vapor of solvent, for example, steam. Note, in this specification, the above vapor of solvent will be referred “solvent vapor”, hereinafter. According to this cleaning (etching) method, the processing gas, for example, ozone gas is supplied to the wafers accommodated in a closed processing container where the resist is removed from the wafers.
However, the substrate processing apparatus employing the above-mentioned cleaning method has problems to be solved. First, dewdrops of the solvent vapor are produced in a solvent-vapor nozzle disposed in the processing container, thereby causing sources of bacteria and particles. Second, the dewdrops are scattered to stick to the wafers at the time of ejecting the solvent vapor, thereby causing the wafers to be cleaned with unevenness. Additionally, the solvent vapor is condensed into dewdrops of water that sticks to an upside inner wall of the processing container. Then, the waterdrops fall onto the wafers to cause the sources of particles. Further, the dewdrops of water are scattered into the processing container, causing the wafers to be cleaned with unevenness.
Since the above-mentioned substrate processing apparatus includes a steam generator whose inside pressure is constant (almost atmospheric pressure), there exists a limit in producing the steam. Therefore, under a situation that an interior of the processing container is pressurized more than the atmospheric pressure, then a problem arises in that the quantity of solvent vapor to be supplied into the processing container decreases, so that the processing capability of the apparatus itself is lowered.